Oxidation of ethers using aldehyde-activated catalysts



Feb. 21, 195o n. c. HULL 2,497,889

OXIDATION OF THERS USING ALDEHYDE-ACTIYATED CTALYSTS Filed March 26,1948 F560 L//YE wma/Bum@ l V Q PLATE Y 36, E a ,f ATE@ Fifa mams/@MM mfrmoll/v6 M50/UM omer 01m/zip f2 DAV/D AC. .HULL

INVENTOR Patented Feb. 2l, 1950 OXIDATION 0F ETHERS USING ALDEHYDE-ACTIVATED CATALYSTS David C. Hull, Kingsport, Tenn., assigner to EastmanKodak Company, Rochester, N. Y., a corporation of'New Jersey ApplicationMarch 26, 1948, Serial No.. 17,346

6 Claims. l

This invention relates to the liquid phase cata lytic oxidation ofaliphatic andl aromatic compounds containing ether linkages and more particularly to the oxidation, by means` of aldehydeactivated metalcatalysts., of' others and acetals typied by such compounds as diethylother, diethyl acetal, dibenzyl ether and the like to acids such asacetic, benzoic and others.

For many yearsin the carrying out of oxidations such as the conversionof. various aliphatic alcohols to the correspondingy acids; it was.necesn sary to employ a roundaboutand indirect procedure involving amultiplicity of steps and 0.0mplicated apparatus; For example,v in the.conversion of ethyl alcohol to acetic, acid it was` the practice nrst tooxidize the .alcoholy to acetaldes hyde in one step and then, by aseparate stop, t0 oxidize the aldehyfde to the acid. In later years agreatly improved and far more. economical technique has been developed,whereby the alcohol may be converted directly, at relatively lowtemperature andA pressure, into the corresponding acid without thenecessity of a. separate procedure for first obtaining: the aldehyde.For ex,- ample, in my United States PatentsNos.y 2,287,803; 2,353,157;2,353,158; 2,853,159: 2,353,160; 2,425,- 878; 2,425,879; 2,425,880;2,425,881; 2,425,882, I have an improved process wherein an alcohol,such as ethyl alcohol, may be. converted directly 'to acetic acid byoxidizing the alcohol in the liquid phase byl means of oxygen or anoxygencontaining eas in the presence of certain metal catalystsdissolved in an aliphatic acidand maintained in an active state throughthe agency of a continuous supply of aldehyde, This. process has provedto be extremely effective and economical for the production of aliphaticacids.

:The catalytic oxidation o f other organic compounds employing asomewhat similar technique,

although operated, in general, under conditions.

whichdiier substantially from the low temperature processes described`in my above-mentioned patents, has been applied to various aliphatic,alicyclic and aromatic ketones, including acetone, methyl ethyl ketone,cyclohexanone. methyl cyclohexanone and acetophenone to convert them tomonobasic and dibasic acids such as acetic, propionic, adipic, methyladipic and benzoic acids. Such a process is described in Flemming et al.2,005,183.

In Patent 2,223,493 Loder has described the liquid phase catalytic.oxidation of cyclic saturated hydrocarbons such as cyclohexane,cyclopentane, cyclobutane and their substituteddcriyatives to obtain thecorresponding` aliphatic dlbaslc acids, 55

such as adipic,; glutaric and succinic. In Patent 2,223,494. Loderdescribes asimilar process for converting cyclic saturatedhydrocarbonsto cyclic alcohols and ketones, while in Patent 2,265,948. he describesa process involving conversion of. open chain aliphatic hydrocarbons to4acids, ketones, esters and alcohols. l

A further extension of the broad concept of oxidizing organic compoundsin the liquid phase is described lby Loder in Patent 2,245,523, in.which reference is made to, the, oxidation of alkyl-substituted aromaticcompounds such as. ethyl bcn,

` zene, toluene: and thexylenes tothe` corresponding aromatic acids suchas benzolc, toluic, phthalic and the like. A similar but, morefspecincprocess is. disclosed in the patent to Henke 2,276,774.`

To the best of my knowlcdge-andbelief, none of; the Workers in thefield. to which the present invention relates has recognized the factthat compounds with ether linkages such as the Sirnf ple and` mixedaliphatic others and acetals or the aromatic ethers may be converted to.aliphatic and aromatic acids by applying the principle of aldehydeactivation to such oxidations. Further.- more, not only have none ofthese` researchersl rec,- ognized` or appliedfthe principle of aldehydeactivation to such oxidations, but they also have operated underrelatively high temperature con.- ditions and obtained relatively lowyields of their respective products.

The present invention has for .its principal ob,- ject to provide aprocess for the economical, er.- cient conversion of aliphatic andaromatic compounds containing ether linkages to acids. A further objectis to provide a process whereby compounds such as diethyl ether,difnormal propyl ether, di-normalbuty1 ether, the` dicthyl acetal ofacetaldehyde, the diethyl. acetal of benz.- aldehyde and various othercompounds contain*- ing ether linkages maybe converted to: the cor.-respondng carboxylic acids. A still further object is to provide aprocess whereby such come pounds may be directlyy oxidized to thedesired products in a single step. Another object iS. to provide aprocess for oxidizinasuch ether-type compounds to valuable acid productsin a man;- nerwhich is both eicient and economical and may be carriedout with a minmumof procedural steps. Other objects will appearhereinafter,

These objectsy are accomplished by the following invention which, in itsbroader aspects, comprises rst preparing an active catalyst solution bydissolving an appropriate metal, metal. oxide or other suitable-metalcompoundin an. aliphatic acid, such as acetic acid, treating thesolution with an oxygen-containing gas and simultaneously adding analdehyde such as acetaldehyde, thereby to bring the metal catalyst intoa highly active state, and thereafter feeding the ether or compoundcontaining an ether linkage, together with an excess of oxygen, into thecatalyst solution while maintaining the catalyst in the solution in anactive state by continuously adding aldehyde. In accordance with theinvention, the solution is maintained under such conditions oftemperature and pressure that the solution is maintained in the liquidphase and the ethel` or compound containing an ether linkage inthesolution is directly converted to the desired acid. For example, bymaintaining a body of active catalyst solution in an appropriate vesselat a temperature within the range of -5 C. and 90 C. and approximatelyatmospheric pressure and continuously adding diethyl ether, acetaldehydeand oxygen or air to the solution, I obtain substantial yields of aceticacid. Likewise, other ethers as well as various aeetals and othercompounds containing ether linkages may be converted to acetic acid andvarious other corresponding acids.

In the following examples and description, I have set forth several ofthe preferred embodiments of my invention, but they are included merelyfor purposes of illustration and not as a limitation thereof.

The single gure of the drawing represents one form of apparatus whichmay be employed for the practice of my invention. Other suitable formsof apparatus which may be employed for the carrying out of such aprocess are illustrated in my above-mentioned patents for example,Patents 2,287,803 and 2,353,157.

My invention will be more fully understood by a preliminary discussionof the preparation and the composition of my improved catalyst solutionsand the general conditions under which my process is operated.

As indicated, I employ what I have described as an aldehyde-activatedmetal catalyst solution. Such a solution can appropriately be prepared,-by dissolving a suitable catalyst metal or one of its aliphaticacid-soluble oxides, salts or other compound in an aliphatic acid suchas acetic, propionic or butyric acid. While in accordance with myinvention, I may employ almost any metal which will produce metallicions in solution, I have found cobalt to be an especially valuablecatalyst. In the same class with cobalt may be mentioned manganese,iron, nickel and copper. Other metals which may be employed as catalystwith substantially equal facility are lithium, beryllium sodium,potassium, rubidium, caesium, calcium, strontium, barium, magnesium,zinc, aluminum, scandium, yttrium, lanthanum, neoytterbium, gallium,indium, thallium, cerium, rutheniurn, rhodium, palladium, osmium,iridium, platinum, gold, tin, antimony, mercury, lead, chromium,molybdenum, tungsten, uranium, tantalum, vanadium, columbium (niobium)titanium, thorium, neodymium, praseodymium, illinium, samarium, holmium,europium, erbium, gadolinium, thulium, terbium, dysprosium, andlutecium.

While in general I prefer to employ a single metal as the catalyst andin the form of one of its oxides, salts or other compound which iseasily soluble in the aliphatic acid selected as the solvent medium, Imay, if desired, employ a plurality of such metals. For example, while Iprefer to C0 (C2H302) 2.4H2O

4 in glacial acetic acid, I may employ a plurality of metals in the formof their acetates, propionates or butyrates, or in the form of oxideswhich form the corresponding aliphatic acid salts in the acid solution.Likewise, while I prefer to use acetic acid alone as the solvent, I mayemploy aliphatic acids such as acetic, propionic, butyric, and the like,either singly or in various combinations one with another.

As to the matter of concentration, I may dissolve the catalyst metal inthe acid to produce solutions containing anywhere from 0.10% to 8% ofthe metal salt, although, in general, I prefer to keep within the rangeof 5% to 6%. Likewise, although I prefer to dissolve the catalyst inanhydrous acid, a more dilute acid may be employed. In general, I havefound that, in use, more satisfactory yields of product are obtained ifthe acid concentration of the catalyst solution is at all timesmaintained at approximately 85% or above.

Once the catalyst solution has been prepared as above described andcharged into a suitable reaction vessel, it is brought into a highlyactive or activated condition by simultaneously feeding in an aliphaticaldehyde, such as acetaldehyde, and oxygen or an oxygen-containing gasat such a rate and at such a temperature as to cause the catalyst tobecome and remain active, a condition usually initially indicated by achange in color of the original solution. The oxygen feed is regulatedto provide a slight excess of oxygen over and above that required forthe oxidation reaction, such excess being indicated by the presence of afew per cent of oxygen in the gaseous eliiuents from the process. Itwill, of course, be understood that such matters as feed rates ofaldehyde and oxygen, temperature and the like, in general, have to bedetermined for each pal?- ticular catalyst and with reference to thecompound to be oxidized. In the case of a cobalt catalyst in aceticacid, the original solution, which is pink, changes to green uponactivation, indicating that the cobalt ions have changed from a lower toa higher state of valence, that is, from the cobaltous to the cobalticstate and that the solution is in the desired catalytically activecondition.

While air is the most economical source of oxygen, I may employ anysuitable oxygen-containing gas such as pure oxygen, ozone, or mixturesof such gases with inert gaseous diluents. Likewise, although I preferto use acetaldehyde, I may employ other aliphatic aldehydes such aspropionaldehyde, butyraldehyde and the like, all

of which aldehydes may be employed singly orr in various combinationsone with another. In general, the aldehyde feed will be so regulated asto maintain .1% to 5% of the aldehyde in the reaction liquid.

While in some cases the catalyst solution will become active merely uponintroduction of the aldehyde and blowing with air or oxygen at ordinaryatmospheric temperatures, it may be necessary to heat the solutionmoderately, say, to a temperature in the vicinity of 50-60" C. in orderto initiate catalyst activity.

As to the matter of temperature, I may oxidize ethers and ether typecompounds in accordance with my invention at a temperature within therange of 5 C. to 150 C., although I prefer to operate in the vicinity ofC. to 110 C. In general, high temperatures, that is, temperatures inexcess of the boiling point of the solvent or product, are to be-avoidedinthe .interest of preciuding degradation of reactants or products, vorlosses by evaporation, polymerization or like phenomena. In view of thefact thatthe oxidation reactions rhere involved are exothermic incharacter, it is usually necessary continuously to cool the reactionmedium in order to keep the temperature within the desired limits, toprevent excessive loss oi reactants by evaporation and to preclude thepossibility of the reaction` becoming too greatly accelerated. On theother hand, under certain circumstances, it may be necessary actual-lyto supply heat, as, for example, in the case of irst starting theprocess, in order to initiate catalyst activity.

As to pressure, while I prefer to operate at atmospheric pressure', oreven below, I may opcrate at pressures as high as 3 4 atmospheres ormore. Use of pressures above atmospheric in general permits operation athigher temperatures. It: will' of course be understood that thevtemperature and pressure will vary according to the requirements of theparticular material undergoing oxidation, the rate of feed of theseveral reactants and with other variables, the control. of which. iswithin theV skill of the trained chemist or chemical engineer.

It will, of course, be understood that in oxidizing ethers or ether typecompounds in accordance with my invention the oxygen supplied bycontinuous introduction of airor other oxygen-containing gas, asexplained above, is the fundamental sour-ce of oxygen for the oxidationreaction. The chief reaction product will be an aliphatic acid such asacetic, propionic, butyric, benzoic, etc., the particular acid of coursedepending on the particular compound oxidized. For example, diethylether may thus be oxidized to acetic acid, di-normal propyl ether topropionic acid, di-normal butyl ether to acetic, propionic and butyri-cacids, dibenzyl ether to benzoic acid, and so on. In a similar manner,various acetals may likewisefbe converted to acids. For example, acetal(the di-ethyl acetal or acetaldehyde) may bel converted to` acetic acid,the di-ethyl acetal of benzaldehyde to benzoic acid and acetic acid.

My invention will new be more clearly understood by reference to apractical operation which may be conveniently carriedout in an apparatus'such as that illustrated in the single figure of the drawing.

The numeral I designates an oxidationunit which mayvv consist of aplurality of anged stainless steel tubes of six-inch inside diameter andapproximately ten feet' long, or any other convenient size orproportions, superimposed one:l on top of the other and bolted together,the main sectionsbeing represented by numerals 2, 3, 4 andA 5. Eachsection is provided with a suitable coolngmeans which may take the formof an internal centrally disposed stainlesssteel' coil suchr as coil 6of section 5, of one-half inch or other appropriate inside diameter,each coil being supplied with cooling medium, such as water throughinlet 'I and emerging therefrom through outlet 8'. Each section is alsosupplied with a thermometer, as show-n, inserted through the walll ofeach section by means of a thermometer well (not shown).

'I-helowermost section of the oxidation unit consists. of a tubularstainless steel member 9` of the same inside diameter as the upperseetions'of the unit, flanged? at the top and closed at the bottom. Tosection 9 is connected inlet conduit I-, owof liquid through which iscontrolled by valve II. Connected into conduit IIJf' i's valved'aldiehyde-feed conduit I2 and another'valvedcon- 6 duit I3` forsupplying the material to be oxidized to the oxidation unit. While thevalves in these iieed lines may be so operated as to provide a regulatedor metered ow of materials to the unit, a somewhat more convenientmethod is to provide rotameters or other metering devices for thispurpose.

Section 9 has tapped into its lower closed end another inlet conduit I4into which is connected air inlet conduit I5, flow oi air or otheroxygencontaining gas through which is lcontrolled by valve I6. ConduitIllV is extended beyond its junction with conduit I5 as shown, theextension being equipped with a valve II to provide a means for drainingthe unit when not in use or between successive runs.

A perforated diffusion plate is inserted and bolted in place between thelower flange of section 2` and the flanged top of bottom section 9 toprovide a means of evenly distributing the liquidgaseous mixture whichenters the bottom of the unit.

The topmost portion of the oxidation unit may conveniently comprisethree sections I8, I9` and 2U, each of which is flanged and boltedtogether as previously described. A distributor plate, which may includea bubble cup and downcomer, is positionedv between the upper flange ofsection 5 and the lower ilange of section I8. To sections I8' and I9`there is connected .a high-pressure sight glass. 2'I for' indicating thelevel of liquid in the upper part of the unit.

The upper closed end of section 2li is provided with an outlet conduit22 adapted to conduct vapors and gas evolved from the top of the unit tocyclone separator 23' where any entrained liquid is separated from themixture and conveyed back into the upper part of the oxidation unit at.section I8 througlr conduit 2d, the latter being so formed at its end`as to provide a liquid seal in proximity to its junction with sectionI3.

Cyclone separator '23 is also provided with an outlet conduit 2li` whichconveys gaseous and vaporous materials to water-cooled condenser 25oiappropriate size and design,. cooling medium for which is suppliedVthrough inlet 2?- and emerges through outlet 2S. Condenser 2'5 is alsoconnected through conduit 23' and sight glass 3.9i to product receiverSI', the latter also being provided withv a sight glass 32 forindicating the level therein. The product receiver is also equipped withvalved conduit 3.3" for withdrawing product therefrom as desired.

Vapors not condensed in condenser 26 may nd their wayin thedirectionindicated by the arrows, through conduits 34, 35 andt, into thebottomfof scrubber 3l which may take the form of a stainless steelf tubeof appropriate diameter packed `with a liquid distributing material suchas berl saddles or Rasehig rings. scrubber 37d is provided near itsupper closed end with conduit 38 through which glacial acetic acid -issupplied in metered amounts passing in countercurrent to the vapore gasstream ascending in 3l and thereby dissolving out any portions ofproducts or reactants which may have escaped entrapment in separator[2.3 or condenser 2B.

TheV lower end oi scrubber 3l is connected, through conduit 351., sightglass S9 and conduit 40 with bottom` section 9 of the oxidation unit.Conduit 40' may be provided with liquid seal 4I through which theglacial acetic acid from scrubber 3T may be fed. to the oxidation unitto maintain the acid` content ci the reaction mixture at the desiredvalue.

Scr'ubber 31 is also provided at its upper end with a vapor or gasoutlet conduit 42 connected as shown to the lower portion 43 of waterscrubber 44 through junction with conduit 45, which also connects theupper part of scrub receiver 45 with the water scrubber. Means is thusprovided through conduit 45 for permitting any entrapped gases or vaporsto escape from the scrub receiver into the water scrubber. The scrubreceiver is equipped with sight glass 4l and a valved outlet conduit 48for withdrawing material therefrom as desired. The scrub receiver isalso directly connected to water scrubber by means of conduit 49.

The Water scrubber has connected to its upper end a valved water feedline 50 and is also provided with outlet conduit 5| which provides meansfor escape of non-condensables from the system. This conduit 5| isprovided with jet valve 52 and is also provided with auxiliary pressurecontrol means through the agency of conduit 53 provided with pressurecontrol valve 54.

The operation of the apparatus when used to carry out the process of myinvention will be apparent on inspection. In starting oxidation unit 4is lled somewhat less than full with catalyst solution, which mayconveniently take the form of a 3% solution of cobaltous acetate inglacial acetic acid. Air valve |5 is opened slightly and aldehyde feedis put on the unit by opening the valve in feed line I2. It will, ofcourse, be understood that a suitable cooling medium such as water issupplied to the several coils of the unit and that the thermometers arein place in the respective thermometer wells for taking readings of thetemperature of the solution.

If the catalyst solution does not become active, as indicated by lchangein color from pink to green, after the elapse of several hours, it maybe necessary to supply steam to the coils instead of cooling medium thusto raise the temperature to approximately C. When the catalyst hasbecome active, it is generally desirable to add more cobalt acetate tobring the yconcentration up to approximately 6%. The amount of catalystdissolved in the original solution will vary, not only with theparticular catalyst selected, but also -with the temperature and variousother conditions. Suiiice it to say that a few per cent of the materialis generally sufficient for effective operation.

Once the catalyst has been activated, the material to be oxidized isintroduced into the oxidation unit through conduit I3 and the aldehydeand air feeds are adjusted so as to provide the proper proportion ofeach material to perform their respective functions. In general, therate of aldehyde introduction will be controlled so as to maintain thecatalyst at all times in an active condition, while the rate of oxygenfeed will be so regulated as to provide a slight excess of oxygen overand above that actually required for oxidation of the material beingconverted, as indicated by a few per cent of free oxygen in theeflluents from the process.

Assuming the material to be oxidized, and aldehyde and air or oxygen,are being continuously fed, oxidation product will be vaporized andcontinuously conveyed out of the unit through Iconduit 22. material alsopasses out of the device along with the product, the liquid portionsbeing separated from the gaseous or vaporous portions in cycloneseparator 23 and eventually returned to the zone of oxidation throughconduit 24.

A certain amount of gaseous and liquid eso The major portion of thecondensable vapors, consisting mainly of the products of oxidation. arecondensed in condenser 26 and find their way into product receiver 3|from which they are continuously removed at such a volume rate as tomaintain the proper liquid level in the oxidation unit. Theuncondensable gases and vapors are conveyed through conduits 34, `35 and36 into acid scrubber `3l, passing upwardly in countercurrent to astream of glacial acetic acid. Any lvaporized materials which haveescaped condensation in condenser 26 are thus dissolved in the aceticacid and returned to the oxidation unit via conduit 40. The amount ofacid thus introduced into the unit is so regulated as to maintain theacid concentraf tion in the reaction liquid at approximately or above,it having been found that this is an acid concentration, which, ingeneral, gives the most satisfactory operation.

Non-condensable gases such as carbon dioxide and nitrogen (from air, ifair is used as the source of oxygen) emerges from the top of scrubber 31through conduit 42 and eventually into water scrubber 44, where theymeet a down-coming stream of water, introduced through conduit 50, whichdissolves out any -water-soluble values which may have escaped previousseparation steps. Non-'condensables pass out of the system through valve52.

The product of the process, which may be in the form of a more or lessdilute acid or other oxidation product, may be removed from productreceiver 3| and conveyed to any desired concentrating or purifying stepsfor conversion into the desired concentrated acid or other product.Likewise, the acid or other materials which have been scrubbed out ofthe vapor-gas stream passing through scrubber 44 may be removed fromscrub receiver 4G through valved conduit 48 and treated in anyappropriate manner for recovery of the dissolved materials.

As to the matter of temperature, I may conveniently carry out oxidationsin accordance with my process, when operated at atmospheric pressure,within the range of 5 C. to 90 C. Since the reactions involved areexothermic, it is generally necessary continuously to supply a coolingmedium to the coils of the oxidation unit in order to maintain thetemperature within the indicated limits. However, in some cases, as forexample, in oxidizing materials of high boiling points, 0r inaccelerating the oxidation reaction, it may be desired to employ highertemperatures thanthose indicated. When such higher temperatures areemployed, pressures in excess of atmospheric will be desirable in orderto prevent boiling away, either of the acetic or other aliphatic acidcatalyst solvent or of the product of the reaction itself. Whenemploying apparatus such as described herein for the carrying out ofoxidation reactions at higher temperatures, say in the range of C. toC., it will be understood that valves 52 and 54 rwill be closed andprovision made for maintaining the desired pressure in the system.Pressure operation will of course require that reactants and scrubbingmedia be introduced under a pressure sufficient to compensate or balancethe pressure existing in the system. While the pressure may under suchcircumstances vary over a wide range, depending on the temperature it isdesired to maintain in the oxidation zone and on various other factors,in general pressures ranging from atmospheric to 3 to 4 atmospheres `aresatisfactory.

75 My invention will be more fully understood by freference to ianumberl-of specific examples illus,-

trating typical conversionscarried out in accord- .'ance therewith.

Example I.-Oidation -of diethylether to acetic acid A catalyst solutionwas prepared by dissolving cobalt acetate in acetic acid in such anamount Aas to obtain 3% concentration of the cobalt salt in the acid.This solution was fed into an oxidation unit such as that illustrated inthe single figure of the drawing until the unit was approximatelytwothirds full. A small amount o-facetaldehyde was then introduced andair was `also permitted to flow into the bottom of the. unit along withthe aldehyde. Since at ordinary temperature the catalyst did not becomeactive, steam was put on the coils of theunit to bring the solutiontemperature up to approximately 60 C., whereupon the catalyst becameactive as -introducedinto the bottom "of the unit at the Vrate ofapproximately 13D-pounds per hour soas v lto-rnaintain the concentrationof acid in the indicated by a` change in the color ofthe solutom sectionof the unit at the rate of approximately 130 pounds per hour, this rateof acid feed being sufficient to maintain the concentration ofacid-inthereaction mixture at 80 to 85% or higher. By operating underthe above conditions it was found that 32.2% of the diethyl etherintroduced Was converted to acetic acid.y

Example IL Ofcidation of di-normal propyl ether to propionic acidperghouit Glacial acetic acid was introduced into the bottom section ofthe unit ,at a rate of approximately 135 pounds per hour, this being(sufficient to maintain the concentration of acid in the reactionmixture at 85% or. better. By operating under these conditions, 30.1%ofthe di-normal propyl ether introduced was converted .to propionicacid.v

Example IIL- Oxidation of oli-normal butyl ether to acetic, propionicand bui'yric acids A catalyst solution was prepared by dissolving cobaltacetate in acetic acid in such an amount as to obtain approximately a 3%concentration of the cobalt salt. This solution was fed into anoxidation unit, such as that il lustrated in the drawing, until the unitwas approximately 2/3 full. Acetaldehyde feed was then introduced andair was permitted to flow in at the bottom of the unit. After an hour atemperature rise was noticed and water was used on the coils to maintainthe temperature at 60-70 C. After another hour, 3% more cobalt acetatewas added, so as to obtain approximately a 6% concentration of thecobalt salt. After this addition, operation was continued for two hoursmore with acetaldehyde feed alone and with air flowing through the unit,and maintaining the temperature at 60-70" C. At this time di-normalbutyl ether was fed into the unit at a rate of pounds per hour andacetaldehyde at thev rate of reactionmixture at -90%. By operating underthe above conditions it was found that 28% ofthe 'di-normal butyl etherwas converted to butyric acid, 0.5% `topropionic acid and 0.5% to aceticf acid.

Eample TV- Oxidation of diethyl acetal oj acetaldehyde to acetic acid Acatalystsolution was prepared and activated in a manner similar to thatdescribed in Example III. After an activefcatalyst was obtained,

the'diethyl acetalfof acetaldehydewas fed into the unit-at the rate of27 pounds per hour and acetaldehyde at a rate of 21 pounds `per hour.Glacial acetic. acid` was also fed into the unit at the' rate of 135pounds per hour so as to maintain the concentration of acid in thereaction mixture at-85-90%. By analysis of the products from thiscontinuous oxidation it was found that 25% of the diethyl acetal wasconverted to acetic acid.

vExample' V.-Ox idation of dibenzyl etherto Vbeneoic acid A catalystsolution Wasprepared and activated in a manner similar to that describedin .Example rIII. When lthe ycatalyst was in a very active state,dibenzyl ether was fed into the unit at the rate of 39 pounds per hourand Vacetaldehyde at a rate of 44 .pounds per hour. Glacial aceticacidwas also fed into the unitattherate of approximately V pounds perhour solas to maintain the concentration of acid in the catalystsolution. at 85% or above. Operation was` carried `out at 75-80" C., anddue to the fact that benzoic acid will not ldistill at this temperature,it was neclize outV the Abenzoic acid-lter and return the catalystsolution 'to the unit. 'The benzoic acid thus obtained `wasrecrystallized for further purification and then sublimed for finalpurification. By continuous oxidation in this manner, it was found that22.5% of the dibenzyl ether Was converted to benzoic acid.

What I claim is: v 1. A process for the direct oxidation of an organiccompound containing an ether linkage having the graphic formula R-O-Rwherein R and R. each is a radical selected from the group consisting ofthe alkyl and araikyl groups to the corresponding carboxylic acid whichcomprises treating a solution of a metal ion in a lower aliphatic acidwith an aldehyde and a gaseous oxidizing medium to form a catalystsolution, simultaneously introducing material amounts of the ether-typecompound and additional aldehyde into the solution, oxidizing thecontent of ether-type compound of the resulting solution of catalystcompound and aldehyde by treating the solution with gaseous oxidizingmedium, maintaining the solution under temperature and pressureconditions during introduction of the oxidizing medium such that thesolution is maintained in the liquid phase, and thereafter recoveringthe acid produced.

2. A process for y.the direct oxidation of an organic compoundcontaining an ether linkage Vhaving the graphic-formula R-O-R wherein 39pounds per hour. Glacial acid feed was also 75,1% andy R.' each? is aradical selected from the l1 group consisting of the alkyl and aralkylgroups to the corresponding carboxylic acid which comprises treating asolution of a metal ion in a lower aliphatic acid with an aldehyde and agaseous oxidizing medium to form a catalyst solution, simultaneouslyintroducing material amounts of the ether-type compound and additionalaldehyde into the solution, oxidizing the content of ether-type compoundof the resulting solution of catalyst compound and aldehyde by treatingthe solution with a gaseous oxidizing medium, maintaining the solution,during introduction of the oxidizing medium, at a tempera- `ture withinthe range of C. to 150 C. and at a pressure such that the solutionremains in the liquid phase, and thereafter recovering the acidproduced.

3. A process for the direct oxidation of diethyl ether to acetic acidwhich comprises treating a solution of a metal ion in a lower aliphaticacid with an aldehyde and a gaseous oxidizing medium to form a catalystsolution, simultaneously introducing material amounts of the ether andadditional aldehdye into the solution, oxidizing the content of ether ofthe resulting solution of catalyst compound and aldehyde by treating thesolution with a gaseous oxidizing medium, maintaining the solution undertemperature and pressure conditions during introduction of the oxidizingmedium such that the solution is maintained in the liquid phase, andthereafter recovering the acid produced.

4. A process for the direct oxidation of an acetal which comprisestreating a solution of a metal ion in a lower aliphatic acid with analdehyde and a gaseous oxidizing medium to form a catalyst solution,simultaneously introducing material amounts of the acetal and additionalaldehyde into the solution, oxidizing the content of acetal of theresulting solution of catalyst compound and aldehyde by treating thesolution with a gaseous oxidizing medium, maintaining the solution undertemperature and pressure conditions during introduction of the oxidizingmedium such that the solution is maintained in the liquid phase, andthereafter recovering the acid produced.

5. A process for the direct oxidation of diethyl ether to acetic acidwhich comprises dissolving cobalt acetate in acetic acid to obtain anapproximately 3 per cent solution of the cobalt salt in the acid,treating the solution with acetaldehyde and a gaseous oxidizing mediumto form an active catalyst solution, simultaneously introducing materialamounts of diethyl ether and additional acetaldehyde into the solution,oxidizing the content of diethyl ether of the resulting solution bycontinuing to treat the solution with the gaseous oxidizing medium whilemaintaining the solution under a temperature of approximately C. and apressure such that the solution is maintained in the liquid phase andthereafter recovering the acetic acid formed in the oxidation reaction.

6. A process for the direct oxidation of dinormal propyl ether topropionic acid which comprises dissolving cobalt'acetate in acetic acidto obtain an approximately 3 yper cent solution of the cobalt salt inthe acid, treating the solution with acetaldehyde and a gaseousoxidizing medium to form an active catalyst solution, simultaneouslyintroducing material amounts of cli-normal propyl ether and additionalacetaldehyde into the solution, oxidizing the content of di-normalpropyl ether of the resulting solution by continuing to treat thesolution with the gaseous oxidizing medium while maintaining thesolution under a temperature of approximately 60 C. and such a pressurethat the solution is maintained in the liquid phase and thereafterrecovering the propionic acid formed in the oxidation reaction.

DAVID C. HULL.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNTTED STATES PATENTS Number Name Date 2,000,604 Malm May 7, 19352,075,100 Dreyfus Mar. 30, 1937 2,287,803 Hull June 30, 1942 2,307,934Lodel' et al Jan. 12, 1943 2,312,468 Ebel et a1. Mar. 2, 1943 2,421,428Melson June 3, 194'7 OTHER REFERENCES Clover: J. Am. Chem. Soc., vol.44, pp. 1107- 1117 (1922).

Legault et al.: J. Am. Chem. Soc., vol. 64, pp. 1354-1356 (1942).

Grimm et al.: Chem. Abstracts, vol. 38, col. 379 (1944).

1. A PROCESS FOR THE DIRECT OXIDATION OF AN ORGANIC COMPOUND CONTAININGAN ETHER LINKAGE HAVING THE GRAPHIC FORMULA R-O-R'' WHEREIN R AND R''EACH IS A RADICAL SELECTED FROM THE GROUP CONSISTING OF THE ALKYL ANDARALKYL GROUPS TO THE CORRESPONDING CARBOXYLIC ACID WHICH COMPRISESTREATING A SOLUTION OF A METAL ION IN A LOWER ALIPHTIC ACID WITH ANALDEHYDE AND A GASEOUS OXIDIZING MEDIUM TO FORM A CATALYST SOLUTION,SIMULTANEOUSLY INTRODUCING MATERIAL AMOUNTS OF THE ETHER-TYPE COMPOUNDAND ADDITIONAL ALDEHYDE INTO THE SOLUTION, OXIDIZING THE CONTENT OFETHER-TYPE COMPOUND OF THE RESULTING SOLUTION OF CATALYST COMPOUND ANDALDEHYDE BY TREATING THE SOLUTION WITH GASEOUS OXIDIZING MEDIUM,MAINTAINING THE SOLUTION UNDER TEMPERATURE AND PRESSURE CONDITIONSDURING INTRODUCTION OF THE OXIDIZING MEDIUM SUCH THAT THE SOLUTION ISMAINTAINED IN THE LIQUID PHASE, AND THEREAFTER RECOVERING THE ACIDPRODUCED.